The present invention is generally related to fuel-injected internal combustion engines, and, more particularly, the present invention is related to fuel-injected two-stroke engines. Still more particularly, the invention relates to marine propulsion devices including such engines.
Known two-stroke direct fuel injection internal combustion engines include a bowl in the upper surface of the piston and a dome or recess in the lower surface of the cylinder head. It is also known to locate a fuel injector at the top of the dome or recess and to have a spark plug extend into the recess. Fuel spray from the fuel injector may be ignited after the fuel spray bounces off the piston or is otherwise introduced into the combustion chamber.
It is known to provide a direct fuel-injected engine having a combustion chamber configured to provide a squish factor of approximately four-to-one, where squish factor is as subsequently defined herein. See U.S. Pat. No. 5,692,468 assigned to the same assignee of the present invention. It will be appreciated that the engine described in that patent has advantageously contributed to the advancement of internal combustion engines, it would be desirable, however, to provide an improved direct fuel-injected engine having a reduced squish factor to improve scavenging and reduce knock tendencies in high speed operating conditions.
Generally speaking, the present invention fulfills the foregoing needs by providing a direct fuel injection internal combustion engine comprising a cylinder head including a lower surface portion closing an upper end of a cylinder to define a combustion chamber between a piston upper surface and the cylinder head lower surface portion. The lower surface portion has therein an upwardly extending recess. The recess has a lower end which is complementary with the piston surface and an upper end. The lower end of said recess has an area in a plane perpendicular to a longitudinal axis of the cylinder and that area comprises a range from more than 20% to about 65% of the cross-sectional area of the cylinder.
The present invention may further fulfill the foregoing needs by providing a direct fuel injection internal combustion engine comprising an engine block defining a cylinder having a longitudinal axis, an upper end, and a cross-sectional area in a plane perpendicular to that axis. The engine further comprises a piston reciprocally moveable in the cylinder along the axis. A cylinder head includes a lower surface portion closing the upper end of the cylinder to define a combustion chamber between the piston upper surface and the cylinder head lower surface portion. The lower surface portion extends generally perpendicular to the axis and has therein an upwardly extending recess. The recess comprises a conical-shaped recess and has a lower end and an upper end. The lower end of the recess has an area in a plane perpendicular to the axis. The area comprises a predetermined fraction of the cross-sectional area of said cylinder. The fraction is chosen sufficiently high to reduce engine knock during high speed operation of the engine.